nfct: introduce new delta-count mode

To emulate active timeout. This changes default configuration
behavior, needs specifying eventmask to 0 explicitly to work
in polling mode. We have now four mode: event, event nohash,
polling, delta.

* event mode
  propagate nfct at DESTROY event only.
  params required:
    pollinterval:       0 (default)
    hash_enable:        1 (default)
    event_mask:         optional

* event nohash
  propagate nfct at NEW and DESTROY event.
  params required:
    pollinterval:       0 (default)
    hash_enable:        0
    event_mask:         optional

* polling mode
  propagate nfct which is vanished since previous as DESTROY.
  params required:
    pollinterval:       != 0
    hash_enable:        1
    event_mask:         0

* delta mode
  propagate nfct at DESTROY event, and on a regular basis.
  Time when executed on a regular basis may be used as start
  and end timestamp instead of timestamps in nfct.
  params required:
    pollinterval:       != 0
    hash_enable:        1
    event_mask:         != 0 (default, optional)

if reset_count is set to non-zero:
  event:        reset counter befor starting only.
  event nohash: same as event
  polling:      reset counter every polling.
  delta:        same as pollig

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
nfct stats: introduce new input plugin

This patch introduce input plugin which propagates couters
acquired by IPCTNL_MSG_CT_GET_STATS_CPU.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
ipfix: add flowDirection IE

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
nflow9: introduce new NetFlow v9 output plugin

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
filter: add new filter for Netflow ICMP_TYPE

This filter creates ICMP_TYPE Netflow v9 from IPFIX icmpTypeIPv4
and icmpCodeIPv4.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
filter: add new filter for IPFIX time

This filter creates IPFIX_flow(Start|End)MicroSeconds and
IPFIX_flow(Start|End)SysUpTime from "flow.(start|end).sec" and
"flow.(start|end).usec".

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>
filter: add new filter creates ifindex from CTMARK

This filter assigns IPFIX_(ingress|egress)Interface from CTMARK
specified by mark_mask_(in|out) in config.

Signed-off-by: Ken-ichirou MATSUZAWA <chamas@h4.dion.ne.jp>